Pulse demodulator system



July 22, 1952 A. M. I EvlNE 2,604,592

PULSEA DEMODULATOR SYSTEM Filed oct. 21, 1947 tio 1"@ 9 70 G77/E1? CHANNELS 'Patentecl July 22, 1952 l t `PULSE DEMODULATORSYSTEM y v Y Arnold M. Levine; Forest Hius, N. Y1., assignor; tif-'1 mesne assignments, to Federal Telephone and s Radio Corporation, Clifton, N. J.. a corporation of Delaware Application october 21, '19421, serial No. 781,031

I y 1. e This invention relates to pulse demodulation systems andmore particularly to pulse translator or demodulator systems for' the translation or demodulationcf time displaced pulses into other forms'.

In pulse communicationsystems of the type in which intelligence is transmitted by varying the time displacement of.a series of. pulses relative to a given timing position,-various forms of circuits'have been devised for selecting pulses corresponding to a single channel.y andyfor translating thesey selected pulses into other forms of energy. In. previous types of translation the variable time displaced pulses are translated into pulseshaving amplitudes ortime durations corresponding to thetime displacements of the individual pulses. These variations may then be transformedby filtering into the original intelligence wave?. Irrthe translators for translating the pulses into variable time duration signals circuits have generally ;been provided `utilizing multi-vibrators orv trigger tube circuits which do. not lendthemselvesl to compact construction and whichy may befdifcultto controlat sufficient rapidity to'provide ,a precise' timing o rr duration ci' vara-ble duration pulses. f f l y It isV an object-of vmy -inventionto provide-a pulse' translator and/ordemodulator for trans-1 lating pulses of variable time.l displacement into pulses 'of variable time 'duration by providing a control circuit forshunting, inl response to. the time displaced pulses, corresponding substantial-ly' fixed .given-time duration pulses, to translate suon fixed pulsesl into pulses having a duration corresponding to the-timedisplacements of these ,time displaced pulses. Y

According to` ay featurefof my invention pulses may be produced-l in responseftor a marker pulse or by other means, having a substantially constamt time` duration, gthese' pulses' corresponding in number to the-numberfof pulses.l of time displacement energy-an'd overlying in time the positionI of. thesetime displaced pulses. rThese constant time duration pulsesand the time displaced pulses aref applied Acon-jointly to ai circuit vto provide a termination-.forthcfixed pulsesat some interval` intermediateits normal duration to provide-resultant; pulses. having time vdurations. corresponding to the time displacementmodulation of the received pulses. Y Y

In accordance withmy inventionthe combination of the pulses may be effected a gating tube which may serve at the saine time as a selector for theV pulses of a desiredchannel4 of amultiplex pulse system, v,cl'rrcut ier accomplish s calms. (umso- 27) ing thel resultsof myinvention includes alsol subordinate features relating to the shaping ofthe givenduration pulses-forthe purpose of securing the desired output results vand. the complete. system Will `include Iilters forthe reproduction of the` original signal envelope.v Y

vMore specifically the base wave` or selector pulse derived from` the received waves .or produced locally-is nrstpassed through a circuit which by amplification: and clipping Will produce trains of rectangular pulses having a-substantial-ly constant time duration. These pulses are passed through a circuit to suitable shaping and lter apparatus. Inf shunt to the'crcuit passing these constant duration pulses is provided a gating tube, to the grid-cathode circuit of which may bev applied theI rectangular constant duration pulses: This; tubemormally is biased so that it Vwill not-pass the normal channel pulses in the absence lofwtlfieapplication 0f'- this rectangular pulse to" the grid. The channel -pulses arealso applied to the grid vcathodecircuit and the pulses which arrive coincident with the'- rectangular pulse will serve to render the tubeeonductive, cuttingofi" the rectangular pulse atthe-time'of application of the channel pulse.

The above-mentioned and lother features andobjects of thisv invention and the manner of attaining them will become moreapparent and the invention itseli Will be .best understoodby reference to the following description of an embodiment of the invention taken in conjunc` tion with the drawing'v the single figure of vvhicl'i illustrates a preferred embodiment of. myinVen-'ition. In the drawing a multichannel receiver is indicated at l from Whichthe signals receivedon antenna 2l orl fromany suitable lsource are received and demodulated to providepulse enve-` lope output for the Variable pulse Wave. lThis Wave is illustrated `,generally at the curve 3 and may constitute a double marker pulse Il` vand separate: channel pulses 5 and 6. The output Wave from receiver I is appliedy to ai'marker'or'refer-` ence pulse selector and pulse; Shaper' 'l Which serves toselect marker orreference-pulsexll and shape it lto some desi-red `form. The .'output pulses from shaper 'legare applied to a distributor 8 which may be in the form of a; pulse delay Aline tapped at Various timefinterval's corresponding with the separate timing channels of pulseszgf, etc. Fromthe output of distributor 8' are'show'n tapping lines 9, Hlz and H going to the 'separate channel selectors.v and demodulato'rsf. Since the selectors and demodulators for'the various chanindicated by wave -I2 and is supplied over coupling resistors to the input circuit of tube I3. In

the output circuit of tube I3 an inductance coil I4 is provided which serves effectively to steepen the leading and trailingedges of the pulse I2 in the output circuit. Tube I3 may serve as a clipper circuit to clip pulse I2 at the level indicated by dotted line I6 on the curve I2. A rectiiier I may serve to clip pulse I2to eliminate noise near the upper portion' thereof. A rsecond. v by-pass rectifier I1 is provided shunting coil I4 to I c remove any residual negative voltages which may result from the inductive action of coil I4. The

output pulse from tube -I3 is positive and takes a,

rectangular shape as indicated at I8. This pulse v has a substantially constant time duration and in view of the operation `of distributor 8 is properly timed with `respect to the incoming channel pulse so thatit will overlie the time position of a channelvpulsesuch as 5' for example, regardless of its'time displacement. The time duration of pulses I8 is not critical but should be chosen so as not to overlap the time period of any of the other channel pulses. This output pulse is applied over leads I 9 directly to the grid-cathode circuit of a tube 26. The pulse vvis also passed through coupling condenser 2I directly to the anode output circuit of tube 2l). Preferably the pulse as passed through coupling condenser 2I is previously subjected to a voltage divider action throughthe' medium of condensers 22 and 23. Condenser v23 is made variable and is shunted by a resistor 24 so that the resulting pulse passed to condenser 2I may be controlled in shape. Adjustment of condenser'23 changes the slope of the top portion of the output pulse shown at 25 in accordance with the dotted line indications of 26 and 2'I to correct distortion in the pulse or to compensate -for distortion which may occur in succeeding circuits. I

The output-pulses from receiver I are also applied over line 28 to the grid cathode circuit of tube over cathode resistor 29. In the absence of any applied channel pulses, pulses would appear in the output circuitY of tube 20 as trains of pulses of constantduration. However, upon coincidencerv of the selected channel 5 and the pulse.I8 in the grid cathode circuit of tube 20, tube 20 is rendered conductive and the plate voltage therefore is caused to drop, serving to cut oi or Vterminate pulses 25 at a time corresponding to the application of the pulse 5. A time constant circuit -consisting of resistors 38 and a coupling condenser'3I in the output of tube 20 serves to elongate the negative voltage existing at the plate for a periodv corresponding to the maximum remaining time duration of pulses 25 to assure that the entire portion of the pulse occurring subsequently to the application of a channel pulse 5 is eliminated. 'I'hus in the output of the circuit of tube.2 the resultant pulse will appear as indicated at 32. Pulse 32 is clipped at level 33 in a clipper-Shaper circuit 34 to provide output pulses 35 having time duration depending upon the time ofarriv'al kof the channel pulse 5. Thus as the channel pulses 5 are displaced in time due to signal or intelligence modulation, the output pulses 35 will correspondingly vary in width or time duration. These variable time duration pulses 35 may then' be applied to an audio filter 36 to remove the high frequency components and reproduce the original audio frequency wave.- The output Waves from lter 36 may then be applied to any desired utilization circuit 31.

It will be understood that if it is desired furtherl to transmit the wave as a variable pulse duration Wave instead of a time displacement wave, the: output pulse from clipper Shaper 34 may be ap plied directly tojsuch further transmission cir-- cuit... -v ,L .Y 1M T 4 While I have described above the principles of Amy invention in connection with specic apparatus, it is to be clearly understood that this description is made only by way of example and not as aY limitation to thepscope of my invention.

1. A pulse receiver system for receiving a Wave consisting of successive time displaced modulation channelpulses .comprising means for producing a wave of negative pulses time displaced to correspond with the time displaced pulses and of a substantially rectangular form of substantially constant time' duration, voltage divider means for selecting alr predetermined portion of said recjtangular pulses, anelectron discharge tube having anode, cathode and grid electrodes having its anode circuit coupled to the output of said voltage divider means, a coupling circuit for applying each of said 'substantially rectangular pulses .to the grid circuit of said` electron discharge device, said electronl discharge device being normallyv biased beyond cutoff and saidrectangular pulse serving toreduce said bias but being insufllcient in amplitude to render said tube'conductive, a coupling circuity for applying said channel pulses to the grid cathode circuit of said tube wherebyv saidube will be'rendered conductive upon simulA taneousapplication` of a channel pulse and a. rectangular'pulse, said rectangular pulse serving effectively to reduce'said pulse from the output of the voltage divider to zero, and time constant. circuitvmeans inthe output of said electron dis'- charge vdevice for insuring persistence of said cuto'i Vcondition for a period corresponding to the remainingl time duration of said rectangular pulse;

2.-?A system for translating pulses of variable timeY displacement'intopulses of time duration corresponding to the time displacementof the individual pulses comprising means for providing pulses of a given time duration and corresponding in number to and `overlying in time position each ofsaidfpulse's Yof--variab1e time displacement, a transmission path for normally passing said con stant duration l' pulses, a normally inoperative shunting circuit 4coupled to' said transmission path, said shunting circuit having an electron dis# charging device having'v an anode circuit coupled to said transmission path to shunt said path upon conduction of said device and an input grid-cathode circuit to which are simultaneously applied said constantlduration pulsesfand said time displaced pulses to render said electronv discharge device' conductive upon coincidence of such pulses and thereby terminate each of said given duration pulses in accordance with the time position of the corresponding time displaced pulse.

3. A 'system according to claim 2 wherein said shunting Acircuit further includes a time constant circuit having a time'constant at least as great as the remaining time duration of said Vgiven duration pulse to'assure 'that the entire portion of the constant duration pulse, occurring subsequently to` the application of he variable time displaced pulse, is eliminated.

fi. A system according to claim 2 wherein said transmission path further includes a voltage divider in advance of said electron discharge device and coupled to the anode circuit thereof, whereby only such amplitude portion of each of said given time duration pulses is passed by said voltage divider that only when applied to said electron discharge device simultaneously with the application of a variable time displaced pulse, will render said electron discharge device conductive.

5. A system according to claim 4 wherein said voltage divider includes a variable condenser and a shunt resistor to control the shape of said given time'duration pulses and compensate for distortion in the said pulse.

ARNOLD M. LEVINE.

REFERENCES CITED The following references are of record in the le of this patent:

Number Number 6 UNITED STATES PATENTS Name Date l Deloraine Nov. 18, 1941 Butement July 2, 1946 Crosby Aug. 13, 1946 Levy Nov. 30, 1948 Hollabaugh Feb. 22, 1949 Levy Nov. 29, 1949 FOREIGN PATENTS Country a Date Great Britain 1947 

